"""asyncpg 연결 풀 + pgvector 등록.

DB = NAS PostgreSQL 16 단일 SoR (마스터플랜 §0). 스키마 4분할: app / kb / audit / ds.
RLS 이중강제: 커넥션 획득 시 SET LOCAL app.current_role / app.current_ai_view 주입
(deps.py 의 RBAC 의존성과 짝). 여기선 풀 + 헬퍼만 제공한다.
"""

from __future__ import annotations

import json
from contextlib import asynccontextmanager
from typing import Any, AsyncIterator, Optional

import asyncpg

from .config import settings

# 전역 풀 핸들. main.py lifespan 에서 init/close.
_pool: Optional[asyncpg.Pool] = None


async def _init_connection(conn: asyncpg.Connection) -> None:
    """커넥션 단위 코덱 등록.

    - jsonb: dict 직렬화 자동 (asyncpg 기본은 str 반환)
    - vector(1024): pgvector. 런타임 인코딩은 RAG 경로에서 처리(여기선 텍스트 캐스트 허용).
    TODO: pgvector 바이너리 코덱 등록(register_vector) — RAG 라우터 구현 시 BGE-M3 1024d 연동.
    """
    await conn.set_type_codec(
        "jsonb",
        encoder=lambda v: json.dumps(v, ensure_ascii=False),
        decoder=json.loads,
        schema="pg_catalog",
    )
    await conn.set_type_codec(
        "json",
        encoder=lambda v: json.dumps(v, ensure_ascii=False),
        decoder=json.loads,
        schema="pg_catalog",
    )


async def init_pool() -> asyncpg.Pool:
    """풀 생성 (main lifespan startup)."""
    global _pool
    if _pool is not None:
        return _pool
    _pool = await asyncpg.create_pool(
        dsn=settings.database_url,
        min_size=settings.db_pool_min_size,
        max_size=settings.db_pool_max_size,
        command_timeout=settings.db_command_timeout,
        init=_init_connection,
    )
    return _pool


async def close_pool() -> None:
    """풀 종료 (main lifespan shutdown)."""
    global _pool
    if _pool is not None:
        await _pool.close()
        _pool = None


def get_pool() -> asyncpg.Pool:
    """초기화된 풀 반환. lifespan 밖 호출 시 RuntimeError."""
    if _pool is None:
        raise RuntimeError("DB pool not initialized — init_pool() must run in lifespan startup")
    return _pool


@asynccontextmanager
async def acquire(
    *,
    role: Optional[str] = None,
    ai_view: Optional[str] = None,
) -> AsyncIterator[asyncpg.Connection]:
    """커넥션 획득 + RLS 컨텍스트 주입.

    RLS 이중강제 (설계서 §4.1, F-30):
      레이어1 = AI 정보비대칭: app.current_ai_view (visible_to[] WHERE 강제)
      레이어2 = 인간 RBAC×cohort: app.current_role (RLS 정책)
    트랜잭션 내 SET LOCAL 로 주입해 커넥션 풀 재사용 시 누수 방지.

    NOTE: RLS 정책/세션변수는 Phase 0 마이그레이션에서 정의(설계서 §3.3 / §4).
          여기선 변수 주입 계약만 확정.
    """
    pool = get_pool()
    async with pool.acquire() as conn:
        async with conn.transaction():
            if role is not None:
                await conn.execute("SELECT set_config('app.current_role', $1, true)", role)
            if ai_view is not None:
                await conn.execute("SELECT set_config('app.current_ai_view', $1, true)", ai_view)
            yield conn


async def healthcheck() -> bool:
    """SELECT 1 핑. /health 에서 사용."""
    try:
        pool = get_pool()
        async with pool.acquire() as conn:
            val = await conn.fetchval("SELECT 1")
            return val == 1
    except Exception:
        return False


async def fetch(query: str, *args: Any, role: Optional[str] = None, ai_view: Optional[str] = None):
    async with acquire(role=role, ai_view=ai_view) as conn:
        return await conn.fetch(query, *args)


async def fetchrow(
    query: str, *args: Any, role: Optional[str] = None, ai_view: Optional[str] = None
):
    async with acquire(role=role, ai_view=ai_view) as conn:
        return await conn.fetchrow(query, *args)


async def execute(
    query: str, *args: Any, role: Optional[str] = None, ai_view: Optional[str] = None
) -> str:
    async with acquire(role=role, ai_view=ai_view) as conn:
        return await conn.execute(query, *args)